IHttpServer::DispenseContainer Method
Returns a context container that may be dispensed.
Syntax
virtual IDispensedHttpModuleContextContainer* DispenseContainer(
VOID
) = 0;
Parameters
This method takes no parameters.
Return Value
A pointer to an IDispensedHttpModuleContextContainer.
Remarks
IHttpServer implementers will typically return a new``IDispensedHttpModuleContextContainer that will call delete on itself when the IDispensedHttpModuleContextContainer::ReleaseContainer method is called.
Example
The following code example demonstrates how to create a global module that listens for GL_CACHE_OPERATION events. This module defines a custom IHttpStoredContext class and then calls the DispenseContainer method with a new pointer to that custom class. The example then writes the custom data to the Event Viewer.
Caution
IIS 7 generates a large number of events in the Event Viewer. To avoid a log overflow error in a production environment, you should generally avoid writing cache information to the event log. For demonstration purposes, this code example writes an entry to the Event Viewer in debug mode only.
#pragma warning( disable : 4290 )
#pragma warning( disable : 4530 )
#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <tchar.h>
#include <initguid.h>
#include <httptrace.h>
#include <httpserv.h>
#include <httpcach.h>
#include <string>
using namespace std;
// The CConvert class mirrors the Convert class that is
// defined in the .NET Framework. It converts primitives
// and other data types to wstring types.
class CConvert
{
public:
// The ToByteString converts a double-byte
// character string to a single-byte string.
// str: the double-byte string to convert.
// return: a single-byte string copied from str.
static string ToByteString(const wstring& str)
{
// Get the length of the
// double-byte string.
size_t length = str.length();
// Create a temporary char pointer.
char* byteChar = new char[length+1];
byteChar[0] = '\0';
// Copy the double-byte character string
// into the single-byte string.
size_t charsReturned = 0;
wcstombs_s(&charsReturned, byteChar,
length+1, str.c_str(), length+1);
// Create a string to return.
string retString = byteChar;
// Delete the temporary string and
// set that string to NULL.
delete[] byteChar;
byteChar = NULL;
// Return the single-byte string.
return retString;
}
};
// The CEventWriter class writes XML
// documents and strings to the event log.
class CEventWriter
{
public:
// Creates the CEventWriter class.
// name: the name of the
// event log to open.
CEventWriter(const wstring& name)
{
#ifdef UNICODE
m_eventLog = RegisterEventSource(NULL, name.c_str());
#else
string multiName = CConvert::ToByteString(name);
m_eventLog = RegisterEventSource(NULL, multiName.c_str());
#endif
}
// Creates the destructor for the
// CEventWriter class. This destructor
// closes the HANDLE to the event
// log if that HANDLE is open.
virtual ~CEventWriter()
{
// If the HANDLE to the event
// log is open, close it.
if (NULL != m_eventLog)
{
// Deregister the event log HANDLE.
DeregisterEventSource(m_eventLog);
// Set the HANDLE to NULL.
m_eventLog = NULL;
}
}
// The ReportInfo method writes
// a wstring to the event log.
// info: the wstring to write.
// return: true if the event log is written.
BOOL ReportInfo(const wstring& info)
{
return ReportEvent(EVENTLOG_INFORMATION_TYPE, info);
}
protected:
// The ReportEvent method accepts an event type
// and a wstring, and attempts to write that
// event to the event log.
// type: the type of the event.
// data: the wstring to write to the event log.
// return: true if the event log is written;
// otherwise, false.
BOOL ReportEvent(WORD type, const wstring& data)
{
// If the m_eventLog HANDLE
// is NULL, return false.
if (NULL == m_eventLog)
{
return FALSE;
}
#ifndef _DEBUG
// If the current build is not debug,
// return so the event log is not written.
return TRUE;
#endif
#ifdef UNICODE
// The unicode version of the ReportEvent
// method requires double-byte strings.
PCWSTR arr[1];
arr[0] = data.c_str();
return ::ReportEvent(m_eventLog,
type,
0, 0, NULL, 1,
0, arr, (void*)arr);
#else
// The non-unicode version of the ReportEvent
// method requires single-byte strings.
string multiByte =
CConvert::ToByteString(data);
LPCSTR arr[1];
arr[0] = multiByte.c_str();
return ::ReportEvent(m_eventLog,
type,
0, 0, NULL, 1,
0, arr, (void*)arr);
#endif
}
private:
// Specify the HANDLE to the
// event log for writing.
HANDLE m_eventLog;
};
// The DispensedContext class is a
// custom IHttpStoredContext implementer.
class DispensedContext : public IHttpStoredContext
{
public:
// The public constructor for the
// DispensedContext class.
// Writes to the event log.
DispensedContext() : m_eventWriter(L"IISADMIN")
{
wstring constructor(L"DispensedContext::DispensedContext");
m_eventWriter.ReportInfo(constructor);
}
// Writes trace information to the event log
// for this method.
void Display()
{
wstring className(L"DispensedContext::Display");
m_eventWriter.ReportInfo(className);
}
// The public pure virtual CleanupStoredContext
// method that all instantiable classes implementing
// the IHttpStoredContext must implement.
// This method calls delete on this.
virtual VOID CleanupStoredContext(VOID)
{
wstring className(L"DispensedContext::CleanupStoredContext");
m_eventWriter.ReportInfo(className);
delete this;
}
protected:
// The protected virtual desturctor of
// the DispensedContext class. Clients
// should not call delete directly; rather,
// they should call the CleanupStoredContext
// method. Writes information to the event log.
virtual ~DispensedContext()
{
wstring constructor(L"DispensedContext::~DispensedContext");
m_eventWriter.ReportInfo(constructor);
}
private:
// Specify the private CEventWriter.
CEventWriter m_eventWriter;
};
// The CDispensedContainerModule class extends the
// CGlobalModule class by creating a custom stored
// container that can be disposed.
class CDispensedContainerModule : public CGlobalModule
{
public:
// RegisterGlobalModule is the public
// static method that creates an instance
// of the CDispenseContainerModule class.
// dwServerVersion: the current server version.
// pModuleInfo: the current
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
static HRESULT RegisterGlobalModule
(
DWORD dwServerVersion,
IHttpModuleRegistrationInfo* pModuleInfo,
IHttpServer* pGlobalInfo
)
{
// Both the IHttpServer pointer and the
// IHttpModuleRegistrationInfo pointers
// are necessary for further processing.
if ((NULL == pGlobalInfo) || (NULL == pModuleInfo))
{
return E_INVALIDARG;
}
// Get the id of the module.
HTTP_MODULE_ID moduleId =
pModuleInfo->GetId();
// The HTTP_MODULE_ID cannot be NULL because
// this is needed for calling the SetContext method
// on an IDispensedHttpModuleContextContainer pointer.
if (NULL == moduleId)
{
return E_INVALIDARG;
}
// Create a new CGlobalCacheModule pointer.
CDispensedContainerModule* containerModule =
new CDispensedContainerModule(pGlobalInfo, moduleId);
// Return an out-of-memory error if the
// containerModule is NULL after the
// call to the new operator.
if (NULL == containerModule)
{
return HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
}
// Attempt to set global notification
// for GL_CACHE_OPERATION events
// by using the traceModule as a listener.
HRESULT hr = pModuleInfo->SetGlobalNotifications
(containerModule, GL_CACHE_OPERATION);
// Return the HRESULT from the call to
// the SetGlobalNotifications method.
return hr;
}
// The virtual method that is called
// when a cache operation occurs.
// pProvider: the current ICacheProvider pointer.
// return: GL_NOTIFICATION_CONTINUE.
virtual GLOBAL_NOTIFICATION_STATUS OnGlobalCacheOperation
(
IN ICacheProvider* pProvider
)
{
// Get the current IHttpModuleContextContainer.
IHttpModuleContextContainer* contextContainer =
this->GetModuleContextContainer();
// If the IHttpModuleContextContainer pointer
// is NULL, or the call to create the container
// or the custom context failed,
// return GL_NOTIFICATION_CONTINUE.
if ((NULL == contextContainer) ||
(FAILED(m_hr)))
{
return GL_NOTIFICATION_CONTINUE;
}
// Get the IHttpStoredContext pointer from
// the IHttpModuleContextContainer pointer.
IHttpStoredContext* storedContext =
contextContainer->GetModuleContext(m_moduleId);
// Attempt to safely cast this container
// to a DispensedContext pointer.
DispensedContext* dispensedContext =
dynamic_cast<DispensedContext*>(storedContext);
// If the IHttpStoredContext pointer is
// safely cast to a DispensedContext,
// then ask it to display itself.
if (NULL != dispensedContext)
{
dispensedContext->Display();
}
// Return GL_NOTIFICATION_CONTINUE.
return GL_NOTIFICATION_CONTINUE;
}
// The GetModuleContextContainer method returns the internal
// IDispensedHttpModuleContextContainer pointer that is returned
// from the call into the IHttpServer pointer.
virtual IHttpModuleContextContainer* GetModuleContextContainer(VOID)
{
return m_dispensedContainer;
}
// public pure virtual method that all
// CGlobalModule non-abstract classes must
// implement. This method calls delete on this.
virtual VOID Terminate(VOID)
{
delete this;
}
protected:
// The protected constructor for the
// CDispensedContainerModule class.
// pGlobalInfo: the IHttpServer pointer to use
// for retrieving an IDispensedHttpModuleContextContainer
// pointer by calling the DispenseContainer method.
// moduleId: the current HTTP_MODULE_ID for setting the
// current module context with.
CDispensedContainerModule
(
IHttpServer* pGlobalInfo,
HTTP_MODULE_ID moduleId
)
: m_moduleId(moduleId)
{
// Initialize the internal HRESULT to E_FAIL.
m_hr = E_FAIL;
// Get a container that is dispensed
// from the IHttpServer pointer. By default, the
// IHttpServer implementer creates a new container
// that is both dispensed and synchronized.
m_dispensedContainer =
pGlobalInfo->DispenseContainer();
// Test for NULL on the return value from
// the DispenseContainer method call.
if (NULL != m_dispensedContainer)
{
// Create a new DispensedContext instance
DispensedContext* context =
new DispensedContext;
// If the call to the new operator
// returns NULL, set the HRESULT
// to an out-of-memory error.
if (NULL == context)
{
m_hr = HRESULT_FROM_WIN32(ERROR_NOT_ENOUGH_MEMORY);
}
else
{
// Set the custom module context
// on the dispensed container.
m_hr =
m_dispensedContainer->SetModuleContext(context, m_moduleId);
// If the SetModuleContext method call fails,
// the client of the IHttpStoredContext pointer
// is responsible for cleanup on this data.
if (FAILED(m_hr))
{
context->CleanupStoredContext();
}
}
}
}
// The protected destructor for the
// CDispensedContainerModule class.
// This method calls the Dispose method.
virtual ~CDispensedContainerModule()
{
Dispose();
}
// A protected Dispose method. This method
// calls ReleaseContainer on the internal
// IDispensedHttpModuleContextContainer pointer
// and then sets that pointer to NULL.
void Dispose()
{
// If creating the container and the
// custom IHttpStoredContext was successful,
// call the ReleaseContainer on the
// IDispensedHttpModuleContextContainer pointer.
if (SUCCEEDED(m_hr))
{
// Call release on the container.
m_dispensedContainer->ReleaseContainer();
// Set the container to NULL.
m_dispensedContainer = NULL;
}
}
private:
// Specify the IDispensedHttpModuleContextContainer
// that will be returned when callers call the
// GetModuleContextContainer method.
IDispensedHttpModuleContextContainer* m_dispensedContainer;
// Specify the HTTP_MODULE_ID pointer.
HTTP_MODULE_ID m_moduleId;
// Specify an HRESULT for the values return from attempting
// to create an IDispensedHttpModuleContextContainer pointer.
HRESULT m_hr;
};
// The RegisterModule method is the
// main entry point for the DLL.
// dwServerVersion: the current server version.
// pModuleInfo: the current
// IHttpModuleRegistrationInfo pointer.
// pGlobalInfo: the current IHttpServer pointer.
// return: the value returned by calling the
// CDispenseContainerModule::RegisterGlobalModule
// method.
HRESULT
__stdcall
RegisterModule(
DWORD dwServerVersion,
IHttpModuleRegistrationInfo* pModuleInfo,
IHttpServer* pGlobalInfo
)
{
// Call the static method for initialization.
return CDispensedContainerModule::RegisterGlobalModule
(dwServerVersion,
pModuleInfo,
pGlobalInfo);
}
The above code writes new events to the Event Viewer, where the Data box contains strings similar to the following.
DispensedContext::~DispensedContext
DispensedContext::CleanupStoredContext
DispensedContext::Display
DispensedContext::DispensedContext
Your module must export the RegisterModule function. You can export this function by creating a module definition (.def) file for your project, or you can compile the module by using the /EXPORT:RegisterModule switch. For more information, see Walkthrough: Creating a Request-Level HTTP Module By Using Native Code.
The RegisterModule calling convention must be stdcall. The best way to guarantee this is to explicitly declare RegisterModule with __stdcall.
Requirements
| Type | Description |
|---|---|
| Client | - IIS 7.0 on Windows Vista - IIS 7.5 on Windows 7 - IIS 8.0 on Windows 8 - IIS 10.0 on Windows 10 |
| Server | - IIS 7.0 on Windows Server 2008 - IIS 7.5 on Windows Server 2008 R2 - IIS 8.0 on Windows Server 2012 - IIS 8.5 on Windows Server 2012 R2 - IIS 10.0 on Windows Server 2016 |
| Product | - IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0 - IIS Express 7.5, IIS Express 8.0, IIS Express 10.0 |
| Header | Httpserv.h |
See Also
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